Clearing up the common misconceptions

Ladies, have you ever been in the position where a guy feels he knows what is important to you in a relationship and therfore becomes insecure about himself even though it doesn't matter to you at all? One example of this is when a guy gets anxious over his size and women time and time again say, 'I like you as you are'. It seems like men just cannot accept facts like this, but why? I wonder if you could post any of the other misconceptions that should really stop troubling men, and inturn this should help them be themselves more instead of feeling they aren't good enough.